CN105199540B - Preparation method of fluorosilane-modified HZSM-5 molecular sieve epoxy resin for magnesium-lithium alloy surface coating - Google Patents

Abstract

The present invention is to provide a kind of preparation method of the molecular sieve epoxy resin of silicon fluoride modified HZSM-5 5 for magnesium lithium alloy face coat.1. using Ludox as silicon source, sodium metaaluminate is silicon source, prepares the molecular sieves of ZSM 5 using hydrothermal synthesis method in the basic conditions；2. the molecular sieves of HZSM 5 are obtained by ion exchange, and carries out on this basis silane-modified, modified the molecular sieve surfaces of HZSM 5 using tridecafluoro-n-octyltriethoxysilane, the molecular sieves of HZSM 5 is obtained excellent dispersiveness, hydrophobic and antifouling property；3. the HZSM 5 for continuing to cross silane treatment is molecular sieve doped into epoxy resin-matrix, not only reduce the agglomeration of sieve particle, and tridecafluoro-n-octyltriethoxysilane contains " F ", electronegativity is big, bonding force between molecular sieve and epoxy resin can also be improved, porosity is reduced, strengthens the barrier propterty of coating.

Description

Fluorosilane-modified HZSM-5 molecular sieve epoxy resin for magnesium-lithium alloy surface coating preparation method

technical field

The invention relates to a method for preparing epoxy resin used for magnesium-lithium alloy surface coating.

Background technique

Magnesium-lithium alloy is the lightest metal structural material in the world. It has ultra-low density, high specific strength, outstanding shock absorption performance and excellent electromagnetic shielding performance, making this material the metal structural material with the greatest weight reduction potential. Due to the unique performance advantages of magnesium-lithium alloy, it has a huge potential application space in aerospace, weaponry, 3C industry and some other civilian fields. The addition of lithium improves the disadvantage of ordinary magnesium alloys that are not easily deformed, but at the same time it also causes a significant decrease in the corrosion resistance of the alloy. This disadvantage seriously affects the service life of magnesium-lithium alloys and restricts the application range of magnesium-lithium alloys. Efficient corrosion protection technologies for lithium alloys have long been a goal of the scientific and industrial communities.

Micro-nano particles are a good filler, and the incorporation of micro-nano particles in organic coatings can effectively improve the protective performance of coatings. HZSM-5 molecular sieve has high thermal stability, mechanical stability, chemical stability, corrosion resistance and cation exchange performance. As a crystalline aluminosilicate, HZSM-5 molecular sieve is composed of silicon-oxygen tetrahedrons or aluminum-oxygen tetrahedrons connected by oxygen bridges to form a molecular-sized pore and cavity system, which has the characteristics of sieving molecules and is widely used. It is used in the fields of catalysis, adsorption, separation and ion exchange. However, there is still little research on HZSM-5 molecular sieve in corrosion protection. We hope to incorporate HZSM-5 molecular sieve into epoxy resin coating as a filler to improve the corrosion resistance of the coating.

Molecular sieve particles are small in size and large in specific surface area. It is easy to agglomerate when mixed into epoxy resin, which greatly reduces the mechanical properties and protective properties of organic coatings. Moreover, if directly mixed with molecular sieve, the bonding force between molecular sieve and epoxy resin is relatively weak. Therefore, in order to improve the dispersion of molecular sieves in organic coatings and enhance the bonding force, it is very necessary to modify the surface of molecular sieves. The silane coupling agent has a special structure and is also an environmentally friendly substance. It has different active groups at both ends of its molecular chain. These two groups can interact with organic and inorganic substances respectively. Form a "molecular bridge" between organic and inorganic substances through chemical bonds. Therefore, adding silane-modified molecular sieves to organic coatings can not only significantly reduce the agglomeration phenomenon between additives, improve the mechanical properties of organic coatings (tensile strength, toughness, impact resistance, etc.), but also improve The bonding strength between molecular sieve, epoxy resin and matrix is improved, the shielding performance of the coating is improved, and the corrosion protection performance of the organic film layer on the surface of the magnesium-lithium alloy is improved.

Contents of the invention

The object of the present invention is to provide a method for preparing a fluorosilane-modified HZSM-5 molecular sieve epoxy resin with excellent protection performance for magnesium-lithium alloy surface coating.

The purpose of the present invention is achieved like this:

(1) Mix ZSM-5 with NH ₄ NO ₃ solution, stir at 80°C for 12h, centrifuge and wash the precipitate at 110°C for 24h, burn in a muffle furnace at 540°C for 4h, repeat the above steps three times to obtain HZSM -5;

(2) Take 0.5g~1g HZSM-5, vacuum dry at 100°C for 1h, add 3mL~5mL methanol after cooling, stir at room temperature for 1h, then sonicate for 20min, then add 1mL of tridecafluorooctyltriethoxysilane, stir Centrifuge for 24 hours, and dry the precipitate under vacuum at 50°C to 70°C for 48 hours to obtain fluorosilane-modified HZSM-5 molecular sieve;

(3) According to the ratio of epoxy resin: polyamide = 2:1, solvent: epoxy resin + polyamide = 10% ~ 60%, fluorosilane modified molecular sieve: epoxy resin = 0.2% ~ 20%, first mix Fluorosilane-modified molecular sieves are added to the solvent, mixed with epoxy resin and polyamide by ultrasonication for 10-15 minutes, stirred evenly, and debubbled by ultrasonication, and then aged at room temperature for 20-25 minutes. All ratios are mass ratios.

The present invention may also include:

1. The ZSM-5 is prepared by this method: add NaAlO ₂ to the alkali solution and stir until it is completely dissolved, then drop in the silica sol under continuous stirring, and then add tetrapropylammonium bromide (TPAB) after fully stirring. , use concentrated sulfuric acid to adjust the pH to 10.5-11, stir vigorously at room temperature for 2.5 hours and then slowly stir for 24 hours, then put it into the reaction kettle, react for 24 hours at 180°C, filter with suction, dry at 110°C, grind, and dry at 550°C Roast in a muffle furnace for 3 hours to obtain ZSM-5.

2. The solvent is a mixture of xylene and n-butanol, xylene:n-butanol=7:3 (mass ratio).

The method of using fluorosilane-modified HZSM-5 molecular sieve epoxy resin for the surface coating of magnesium-lithium alloy is as follows: the magnesium-lithium alloy is polished, degreased, alkali washed, washed with water, and air-dried to coat a layer of modified epoxy resin on the surface. permanent epoxy coating. After coating the slices, place them at room temperature for 24 hours, and then place them in an oven at 60°C for 48 hours.

The present invention proposes: ① Use tridecafluorooctyltriethoxysilane to modify HZSM-5 molecular sieve. ②Add the silanized HZSM-5 molecular sieve into the epoxy resin. Preparation of fluorosilane modified HZSM-5 epoxy resin coating.

The main technical characteristics of the present invention: 1. use silica sol as silicon source, sodium metaaluminate as aluminum source, utilize hydrothermal synthesis method to prepare ZSM-5 molecular sieve under alkaline condition; 2. Obtain HZSM-5 molecular sieve by ion exchange, and On this basis, carry out silane modification, use tridecafluorooctyltriethoxysilane to modify the surface of HZSM-5 molecular sieve, so that HZSM-5 molecular sieve can obtain excellent dispersion, hydrophobicity and antifouling performance; ③Continue to silane treatment Doped HZSM-5 molecular sieve into the epoxy resin base, which not only reduces the agglomeration of molecular sieve particles, but also contains "-F" in tridecafluorooctyltriethoxysilane, which has a large electronegativity, and can also improve the molecular sieve Bonding force with epoxy resin, reducing porosity and enhancing the protective performance of the coating.

The invention prepares the fluorosilane-modified HZSM-5 epoxy resin coating on the surface of the magnesium-lithium alloy. This method has the following characteristics. First, the silane coupling agent used, tridecafluorooctyltriethoxysilane, releases low-molecular alcohol after hydrolysis, and the resulting active silanol can be combined with many inorganic and organic substrates. The hydroxyl group, carboxyl group and oxygen-containing group in the compound are bonded, and a self-assembled monomolecular fluorosilicon film layer is formed on the surface of the inorganic material, so that the treated substrate has extremely low surface energy and poor wettability , has excellent protective properties. The second is that this experimental method has a simple operation process and is easy to control, making this method easier to apply to industrial production. The third is that the raw materials used and the reaction process will not produce toxic products, which is green and environmentally friendly. Most importantly, the coating has good corrosion resistance.

Description of drawings

Fig. 1 is the EIS test chart of coating fluorosilane-modified HZSM-5 epoxy resin coating on the surface of magnesium-lithium alloy by the method of the present invention and the epoxy resin coating of HZSM-5 immersed in 3.5% NaCl solution.

detailed description

Technical scheme of the present invention mainly comprises:

(1) The synthesis and silane modification process of ZSM-5 molecular sieve is as follows: completely dissolve a certain amount of alkali (such as NaOH) in deionized water, add an appropriate amount of NaAlO ₂ and stir until completely dissolved, slowly drop into silica sol under constant stirring , after fully stirring evenly, add tetrapropylammonium bromide (TPAB), finally adjust the pH to about 10.5-11 with concentrated sulfuric acid, stir vigorously at room temperature for 2.5h and then slowly stir for 24h, then put it into the reaction kettle, ℃, reacted for 24h, suction filtered, dried at 110℃, ground, and calcined in a muffle furnace at 550℃ for 3h to obtain ZSM-5. Then take an appropriate amount of ZSM-5 and mix it with NH ₄ NO ₃ solution, stir it mechanically for 12 hours in a water bath at 80°C, wash it with centrifugal water for 5 times, put the precipitate in an oven at 110°C for 24 hours, grind it, burn it in a muffle furnace at 540°C for 4 hours, repeat The above steps are performed three times to obtain HZSM-5. Finally, take 0.5g~1g HZSM-5, dry it under vacuum at 100°C for 1h, add 3mL~5mL of methanol to it after cooling, stir at room temperature for 1h, then sonicate for 20min, then add 1mL of tridecafluorooctyl triethoxy to the solution base silane, stirred for 24 hours, centrifuged twice (removing the supernatant), and the precipitate was dried in a vacuum oven at 50°C to 70°C for 48h. The obtained fluorosilane modified HZSM-5 molecular sieve.

(2) The epoxy resin modification process is as follows: epoxy resin, polyamide as curing agent, xylene and n-butanol as solvent, fluorosilane modified molecular sieve (based on the mass of epoxy resin). Epoxy resin: polyamide=2:1, xylene: n-butanol=7:3, solvent: (epoxy resin+polyamide)=10%～60%, fluorosilane modified molecular sieve (based on epoxy resin quality Total) is 0.2% to 20%. First, add fluorosilane-modified molecular sieve to the solvent, mix it with epoxy resin and polyamide by ultrasonication for 10-15 minutes, stir slowly and evenly, remove air bubbles by ultrasonication, and then mature at room temperature for 20-25 minutes.

The technical solutions and effects of the present invention will be further described below in conjunction with the embodiments. However, the particular methodology, formulation and instructions employed are not limiting of the invention.

(1): Synthesis of ZSM-5 molecular sieve by hydrothermal method. First, using silica sol as the silicon source and sodium metaaluminate as the aluminum source, under alkaline conditions, the stoichiometric ratio SiO ₂ :Al ₂ O ₃ :H ₂ O:TPAB:Na ₂ O=2:0.01:150 :0.4:0.73, completely dissolve 7.2g NaOH in 302.5mL deionized water, add 0.82g NaAlO ₂ and stir until completely dissolved, slowly drop in 38.75mL silica sol under continuous stirring, add 13.35g Tetrapropylammonium bromide (TPAB), and finally use concentrated sulfuric acid to adjust the pH to about 10.5-11, stir vigorously at room temperature for 2.5h and then slowly stir for 24h, then put it into a polytetrafluoroethylene-lined reaction kettle, Control at 180°C, react for 24 hours, wait for cooling, filter with suction, dry in an oven at 110°C for 12 hours, grind after cooling, and finally remove the template agent: put the ground powder into a crucible and place it in a muffle furnace at 550°C Roasting for 3h, ZSM-5 is obtained.

(2): Preparation of HZSM-5. Weigh 8g of ZSM-5 and disperse it in 150mL 2mol/L NH ₄ NO ₃ solution, under 80℃ water bath, mechanically stir for 12h, centrifuge and wash 5 times, remove the supernatant and put the obtained sample in an oven at 110℃ 12h, and then burned in a muffle furnace at 540°C for 4h, and repeated the above steps twice to obtain HZSM-5.

(3): Fluorosilane modification of HZSM-5. Take 0.5g~1g HZSM-5, dry it under vacuum at 100℃ for 1h, add 3mL~5mL of methanol to it after cooling, stir at room temperature for 1h, then sonicate for 20min, then add 1mL of tridecafluorooctyltriethoxy to the solution Silane, stirred for 24 hours, centrifuged twice (removing the supernatant), and the obtained sample was dried in a vacuum oven at 50°C to 70°C for 48h.

(4): Preparation of modified epoxy resin coating: epoxy resin, polyamide as curing agent, xylene and n-butanol as solvent, and fluorosilane modified molecular sieve as filler. 4g epoxy resin, 2g polyamide, 0.84g xylene, 0.36g n-butanol, 0.5% silanized molecular sieve (based on epoxy resin mass). The modified molecular sieve was added to the solvent, ultrasonicated for 10 minutes, mixed with epoxy resin and polyamide, stirred slowly, then vacuumed (or ultrasonically) until there were no bubbles in the mixture, and then aged at room temperature for 20 minutes.

(5): The magnesium-lithium alloy is coated with a layer of modified epoxy resin coating on the surface after grinding, degreasing, alkali washing, water washing, and air drying. After coating the slices, place them at room temperature for 24 hours, and then place them in an oven at 60°C for 48 hours.

Adopt the method of the present invention to coat fluorosilane modified HZSM-5 epoxy resin coating and the epoxy resin coating of HZSM-5 on magnesium-lithium alloy surface and dip in 3.5%NaCl solution and test EIS as shown in Figure 1, EIS It is proved that the low-frequency impedance of the epoxy coating doped with tridecafluorooctyltriethoxysilane modified HZSM-5 is one order of magnitude higher than that of the epoxy coating doped with HZSM-5 when the immersion time is 1920h. With the prolongation of immersion time, the low-frequency impedance of fluorosilane-modified 2424h is much higher than that of unmodified 1920h, which shows that the barrier performance of epoxy coating doped with fluorosilane-modified HZSM-5 is greatly improved.

Claims (3)

1. a kind of preparation method of the fluorosilane modified HZSM-5 molecular sieve epoxy resin that is used for magnesium-lithium alloy surface coating is characterized in that: (1) Mix ZSM-5 with NH ₄ NO ₃ solution, stir at 80°C for 12h, centrifuge and wash the precipitate at 110°C for 24h, burn in a muffle furnace at 540°C for 4h, repeat the above steps three times to obtain HZSM -5; (2) Take 0.5g~1g HZSM-5, vacuum dry at 100°C for 1h, add 3mL~5mL methanol after cooling, stir at room temperature for 1h, then sonicate for 20min, then add 1mL of tridecafluorooctyltriethoxysilane, stir Centrifuge for 24 hours, and dry the precipitate under vacuum at 50°C to 70°C for 48 hours to obtain fluorosilane-modified HZSM-5 molecular sieve; (3) According to the ratio of epoxy resin: polyamide = 2:1, solvent: epoxy resin + polyamide = 10% ~ 60%, fluorosilane modified molecular sieve: epoxy resin = 0.2% ~ 20%, first mix Fluorosilane-modified molecular sieves are added to the solvent, mixed with epoxy resin and polyamide by ultrasonication for 10-15 minutes, stirred evenly, then ultrasonically removed air bubbles, and then aged at room temperature for 20-25 minutes, all ratios are mass ratios; The ZSM-5 is prepared by the following method: add _NaAlO to the alkali solution and stir until it is completely dissolved, drop in the silica sol under continuous stirring, add tetrapropylammonium bromide (TPAB) after fully stirring, and use Concentrated sulfuric acid to adjust the pH to 10.5-11, stir vigorously at room temperature for 2.5 hours and then slowly stir for 24 hours, then put it into the reaction kettle, react for 24 hours at 180°C, filter with suction, dry at 110°C, grind, and put it in a muffle at 550°C Roasting in the furnace for 3h, ZSM-5 is obtained. 2. the preparation method of the fluorosilane-modified HZSM-5 molecular sieve epoxy resin that is used for magnesium-lithium alloy surface coating according to claim 1 is characterized in that described solvent is the mixture of xylene and n-butyl alcohol. 3. the preparation method of the fluorosilane-modified HZSM-5 molecular sieve epoxy resin that is used for magnesium-lithium alloy surface coating according to claim 2 is characterized in that the mass ratio=7:3 of xylene and n-butyl alcohol.